For removing extension simply go to:

Profile >> Extensions >> and then hover over the "installed" button next to the extension you want to remove.

Check out this GIF below.

ps. Keep in mind, after removing the extension, its effects to be fully removed, you need to refresh all cards. For that reason, a button pops up next to the extension name that allows you to refresh all cards simultaneously so you don't have to do it one by one.

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